In order for humans to successfully explore beyond the bounds of the Earth, it will be necessary to bring along oxygen for life support and fuel for power. Carrying a sufficient supply of fuel and oxygen for a direct, round trip flight to locations beyond the Moon, however, is not technically feasible since these substances significantly contribute to weight and volume penalties.
As a result, on location oxygen and methane production has been extensively investigated. As is described in U.S. Pat. No. 4,452,676 (incorporated herein by reference), oxygen and methane can be produced in an environment containing abundant amounts of carbon dioxide. Therefore, extraterrestrial bodies, such as asteroids and planets, possessing an abundance of carbon dioxide are potential oxygen and methane production sites. For example, carbon dioxide is indigenous to Mars, equaling about 95.3% of its atmosphere. Therefore, on location methane and oxygen production can be accomplished on Mars.
The oxygen and methane production consists of converting carbon dioxide and hydrogen to methane and water vapor. The methane and water vapor are separated by cooling the methane and water vapor stream such that the water condenses. The condensed water is directed to an electrolyzer where it is electrolyzed to its constituents, hydrogen and oxygen. This hydrogen is recycled for additional conversion of carbon dioxide to water and methane. The oxygen can be stored for use as an oxidant for fuel or utilized for life support.
Meanwhile, the methane is separated into two portions. One portion of the methane is stored as fuel, while the remainder of the methane is introduced to a carbon formation reactor where it is pyrolyzed to its constituents, hydrogen and carbon. This hydrogen is similarly recycled as a reactant for the production of methane and water. The carbon, on the other hand, accumulates on expendable glass packing in the carbon formation reactor as solid carbon.
Although this oxygen and methane production process is an improvement over carrying methane and oxygen as cargo on extraterrestrial flights, limitations relating to the expendables significantly contribute to weight and volume penalties. Here, disposal of the solid carbon and replacement of expendables such as the glass packing are limitations which were not experienced by the prior art.
The methane produced from the carbon dioxide and hydrogen is pyrolyzed to hydrogen and solid carbon which deposits on the glass packing in the carbon formation reactor. Eventually, the accumulated solid carbon increases the pressure drop across the carbon formation reactor to a point where the energy requirements for passing the methane through the reactor become excessive, making further methane pyrolysis impractical. As a result, the solid carbon must be removed and disposed of or stored, and the glass packing must be cleaned or replaced.
Removal of the accumulated solid carbon is a manual procedure which requires cooling the carbon formation reactor to a temperature at which the carbon can be handled, about 45.degree. C. (113.degree. F.), disassembling the carbon formation reactor, physically removing the carbon from the reactor, and replacing the expendable glass packing with a new glass packing. Once the glass packing has been replaced, the reactor must then be reassembled and brought back up to temperature, about 1200.degree. C. (2192.degree. F.), thereby requiring an additional energy expenditure.
If the teachings of U.S. Pat. No. 4,452,676 are employed, oxygen and methane would not be required cargo in a flight to Mars. However, this process is limited in that it requires expendables such as glass packing and containers for storing the glass packing. For example, a return mission from Mars would require the production of 23 metric tons of methane. Such methane production would require 29 m.sup.3 of glass packing for the 17.2 metric tons of carbon produced during pyrolysis. Although the glass packing consumes less volume and weight than carrying oxygen and methane as cargo, it fails to solve the volume and weight problems experienced by the prior art. Also, the carbon coated glass packing must be disposed of, creating a disposal problem.
What is needed in the art is an automated process for the production of oxygen and methane from carbon dioxide and hydrogen that is efficient, does not require expendables, and can be run in a continuous process.